Dozer blade including overload relief means



Oct. 6, 1964 E. R. FRYER DOZER BLADE INCLUDING OVERLOAD RELIEF MEANS 3Sheets-Sheet 1 Filed June 6, 1962 V INVENTOR. {aka a ZZWK BY A TTOR/VEYOct. 6, 1964 E. R. FRYER DOZER BLADE INCLUDING OVERLOAD RELIEF MEANSFiled June 6, 1962 5 Sheets-Sheet 2 ATTORNEY 1964 E. R. FRYER 3,151,406

DOZER BLADE INCLUDING OVERLOAD RELIEF MEANS Filed June 6, 1962 3Sheets-Sheet 3 AT T ORNEY United States Patent() 3,151,466 DGZER BLADEHNQLUDING GVERLOAD RELEEF MEANS Edward R. Fryer, Euciid, Uhio, assignorto General Motors Corporation, Detroit, Mich, a corporation of DelawareFiled June 6, 1962, Ser. No. 206,389 9 Claims. (ill. 37-444) The presentinvention relates .to a dozer assembly particularly adapted for use witha prime mover having a relatively light frame which would be unable towithstand the extreme forces encountered periodically during dozing.

In general, a dozer assembly typically comprises a pair of push arms, orbeams, having one end thereof pivotally connected to a prime mover, suchas a rubber tired or crawler tractor. The lower portion of a dozer bladeis pivotally connected on a horizontal transverse axis to the front endof the push beams so as to extend transversely of and in front of theprime mover. It is common practice to have rigid or manually adjustablestruts extending between each push beam and upper portion of the dozerblade so as to hold the latter in any selected position relative to thepush bearns. Hydraulically operated jacks or a cable operated controlunit is operatively associated with the dozer blade for moving thelatter and its push arms between a lowered dozing position and uppercarry position.

During dozing operations, such a dozer assembly is periodicallysubjected to extremely great forces and stresses due, for example, tothe dozer blade encountering a large boulder or other relativelyimmovable obstruction. Such forces are transmitted by the push beams tothe main frame of the prime mover. Because of this, prime moversdesigned specifically to receive dozer blades are equipped with heavyhigh-strength frames to withstand the maximum forces which might beencountered.

In many instances, especially where overhung scrapers are used, it hasbeen found desirable to mount a dozer blade in front of the tractor sothat a light-duty type dozing operation can be accomplished. It iscommon knowledge that the frame of an overhung tractor normally designedto accept the stresses imposed in a typical scraper application and notnecessarily built to withstand severe bulldozer shock-loading. Hence,unless provision is made for relieving the overloads frequentlyencountered by a dozer blade, the tractor frame could be damaged due tosevere stressing.

Accordingly, one object of the present invention is to provide a dozerassembly having means which permit the dozer blade to trip over anobstacle that would cause extremely large forces and stresses to theframe of a prime mover, and returns the dozer blade to a dozing positionupon clearing the obstacle.

Another object of the present invention is to provide a dozer assemblyhaving fluid operated means for moving a dozer blade between a dozingand carry position and includes means permitting automatic expansion andcontraction of the fluid operated means whenever the dozer blade issubjected to a predetermined force.

The above and other objects are accomplished with a dozer assembly for aprime mover that includes a dozer blade mounted at one end of a push-armwith a hydraulic jack pivotally connected thereto for raising andlowering the dozer blade between a carry position and a dozing positionrespectively. Overload relief means are provided in the hydrauliccircuit connected to the jack for permit ting the latter to expand andcontract whenever the dozer blade is subjected to a predetermined loadso that the blade may raise over an obstacle. Means are associated withthe dozer blade and the push-arm for returning the dozer blade to anormal dozing position once the blade has cleared the obstacle and inthe event of a failure in the hydraulic system when the blade is in acarry position, means are provided for latching the blade to the primemover.

A more complete understanding of the subject invention can be derivedfrom the following description taken in conjunction with the drawings inwhich:

FIGURE 1 is an elevation view showing the present invention incorporatedwith a rubber tired overhung tractor.

FIGURE 2 is a front end view of the tractor shown in FIGURE 1.

FIGURE 3 is an enlarged view of the subject invention with the dozerblade in the various positions assumed after encountering an overloadcondition.

FIGURE 4 shows the dozer blade in a carry position and shows the safetylatch associated with the dozer blade and the tractor vehicle.

FIGURE 5 is a schematic diagram illustrating the fluid circuitryoperating the dozer assembly jacks.

Referring to FIGURES 1 through 3, a dozer assembly 2 incorporat ng thesubject invention is shown mounted to an overhung two-wheeled rubbertired tractor 4 having the usual frame 5 and pivotally connected by aconventional hitch 6 to a scraper bowl frame 4. Inasmuch as the tractorand scraper form no part of this invention, further detail descriptionthereof is omitted and suffice it to say that the components andoperation thereof are conventional.

The dozer assembly 2 comprises a pair of push-arms 10, each of whichconsist of two forwardly diverging strut members 12. The rear end ofeach push-arm 10 is pivotally connected at A to a bracket 14 secured tothe tractor frame 5. The forward end of each push-arm is pivotallyconnected at B to a lower rearward portion of the dozer blade mold board16 to which a cutting edge 18 is secured while a chain 19, securedbetween the tractor frame 5 and the push-arms, limits downward movementof the latter. The forward end of the strut member 12 includes a stopcollar 20 engageable with opposite ends of arcuate stop plates 22secured to the rear portion of the mold board 16. Engagement between thestop collar and the ends of the stop plates limits pivotal movement ofthe dozer on the axis B between a normal dozing position illustrated infull lines and the forwardly tipped positions shown by the phantomlines. A spring 24 is connected between each push-arm '10 and a bracket26 on the rear of the mold board above axis B. The spring memberscontinuously urge the dozer blade to its normal position relative to thepush-arms 10 as limited by the aforementioned stop means. On the otherhand, the springs permit forward tipping of the dozer blade relative toits push-arms and as limited by the aforementioned stop means in amanner to appear hereinafter.

The dozer assembly is lifted and lowered by means of a hydraulicallyoperated double-acting jack 28 which includes the usual piston 36 androd 31 and being pivotally connected at points D and C to the tractorframe and the dozer mold board, respectively. As shown in FIG- URE 5,the hydraulic circuit for operating the jack 28 includes relief valves32 and 34 connected with lines 35 and 37 for exhausting or filling thejack at either the upper or lower side of the piston 36 In addition,both relief valves 32 and 34 are respectively connected by lines 36 and38 to a conventional control valve 40 which selectively supplies fluidpressurized by the pump 42 to either line while returning the fluid to areservoir 44 via a line 4% when in a neutral position. Each relief valveincludesappropriate valving for preventing return flow between the jack2% and control valve 40, but permitting return flow through other lineswhen the fluid pressure in either line 35 or 37 exceeds a predetermineddesign value of the associated relief valve as will be more fullyexplained hereinafter. The reservoir, pump, and control valve areinterconnected by a line 46 while check valves ,5!) and 52 maintainfluid flow in one direction only so as 'to prevent fluid flow towardlines 54 and 56 via the FIGURE 3, it will be noted that pivotconnections A, B,

and C and the jack anchorD are illustrated for four different positionsof forward travel of the vehicle as the mechanism operates to relieveloads or stress beyond any particular design value. Thus, when the jack28 is operatedto lower the dozer assembly 2 into a dozing position, asthe cutting edge '18 digs into the ground, the resistance acting againstthe edge creates a counterclockwise moment about the push-arm 1i pivotalconnection A which causes the push-arms to rotate downwardly to anextreme'position so as to tighten the chain 19. At this time thepush-arms are no longer free to rotate about the pivot axis vA due tothe taut chain and the blade is then disposed in its maximum depthdozing position in dicated by the solid lines in FIGURE 3.

As the Vehcle moves from the solid line position toward position No. 2(indicated by the pivot connections A B C and D the resistance on thedozer blade may vary. If it remains below a predetermined design valueof the overload relief valve 34, the dozer blade remains in its normaldozing position relative to its push-arms under the influence ofsprings24 and due to the fact that the load on the jack 28 is not sufficient toopen the relief valve. If this resistance exceeds such design value, thedozer blade rotates counterclockwise about the pivot axis B since theforce imposed thereon is great'enough to overcome the spring 24 and openrelief valve 34 to permit necessary extension of the jack 28. As seen inthe schematic of FIGURE 5, extension of the jack causes fluid to beredirected from the lower to the upper portion of the piston via theline 37, relief valve 34, and line 35. The lower portion of the jack hasless volume than the upper portion because of the rod 31, and thereforethe deficiency in fluid required to fill the upper portion is providedfrom the return line 48 which is con nected to line 35 through line 54and check valve 5%. As the blade continues to rotate in this manner itapproaches a centered position between the first and second positions.That is, pivot axis B approaches alignment with pivot axes A and C. Ifthe resistance continues, the dozer blade continues, to rotatecounterclockwise about pivot axis B into an overcenter positionindicated by the pivot axes A B and C in which E is just above a linepassing through the points A and C At this time the dozer assemblycollapses. That is, the resistance on the dozer blade rapidly pivots theblade forwardly about axis B and causes push-arms to pivot upwardlyabout axis A. During this action the springs 24 extend and relief valve32 operates to permit the jack 28 to shorten. Referring to FIGURE 5, itcan be seen that the latter occurs when the piston moves in an upwarddirection thereby causing a pressure increase in the fluid located inline 35 so as to open the relief valve 32 and follow a path whichreturns a portion of the fluid to the reservoir 44 through the flowrestrictor 58. The restrictor serves to limit the amount of fluidreturning. to the reservoir through line 69 and therefore the remainderof the fluid returns via the line 56, check valve 52, relief valve 34,and line 37 to the lower side of the jack. At vehicle position No. 3(indicated by the pivot connections A B C and D the blade is freelyrotated about B against the stop collar.

During the forward tipping movement of the dozer blade, the groundresistance to forward travel of the vehicle acts on the inclined surfaceof the moldboard 16 to provide a clockwise movement about the pivot axisA thereby forcing the blade to slide upward and forward over theoverload resistance, such as a large rock or boulder. During thisaction, relief valve 32. is operated to permit further shortening ofjack 28 in a manner as described above. Position No. 4 (indicated by thepivot connections A B C and D shows the dozer blade a vehicle positionafter being forced up and {wot a typical overload mass. Once thisoverload 'is released, the spring 24 in conjunction with the weight ofthe assembly, rotates the blade to its normal position relative to thepush-arm it} in the dozing position. During this return movement of thedozer blade, the extending movement of the jack causes the fluid to flowfrom the lower portion of the jack to the upper portion as describedabove.

It should be apparent that this dozer assembly can encounter variousconditions other than the one described above and still provide overloadrelief. For example, the cutting edge 18 can ride over a portion of aboulder or other obstacle partially protruding above ground levelwithout causing the moldboard to pivot forwardly about pivot point B. Inthis instance, when the vertical force acting against the lower portionof the cutting edge exceeds the design value of the overload reliefvalve 32, the jack would contract and the moldboard would be raisedvertically about pivot A. Once the dozer assembly has cleared theobstacle, the jack can be extended to reposition the moldboard in thenormal dozing position.

FIGURE 4 illustrates the manner in which the dozer assembly 2 is storedin a high lift or carry position when not in use. In addition, a safetylatching arrangement is shown which serves to operate in case ahydraulic failure should occur. Thus the forward end of the vehicleframe 5 is provided with a pair of spaced keepers 62, each having a camsurface 64 for cooperation with a corresponding latch member 66 carriedat the upper edge of the blade and also including a cam surface 68. Asaforementioned, the jack 28 may be operated to lift the dozer assemblyfrom the full line dozing position shown in FIGURE 3 to variousintermediate positions toward the upper or carry position, as shown infull lines in FIGURE'4. As the dozer blade moves from the dozingposition to the carrying position, the members 62 and 66 cam againsteach other and position and dozer blade, as shown in full lines inFIGURE 4. Should a hydraulic failure occur, the dozer blade will dropfrom the full line position to the position shown by the phantom linesat which time the member 66 is held in latching engagement with thekeeper 62 by the spring 24. It should be apparent at this time that ifhydraulic pressure is then reapplied to lower the assembly to the dozingposition, the cam surfaces 64 and 63 pivot the dozer blade forwardlyabout axis B overcoming the force of springs 24. Thereafter, the springs24 return the dozer blade to its normal dozing position relative "topush-arm 10, and jack 28 continues to operate to lower the assembly intodozing position.

Various changes and modifications can be made in the above describedstructure without departing from the spirit of the invention. Therefore,it should be understood that such changes and modifications arecontemplated and the invention is not limited except by the scope of theappended claims.

I claim:

1. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at one end' thereof pivotally mounting the push arm to saidframe, a mold board including a cutting blade, said push arm having asecond pivotal connection at the other end thereof pivotally carryingthe mold board, operating means pivotally connected between the mainframe and the mold board for raising and lowering the mold board to adozing position, said push arm second pivotal connection being locatedto one side of a line passing through the push arm first pivotalconnection and said operating means pivotal connection on the mold boardwhen the latter is in a dozing position, means including the operatingmeans for permitting the second pivotal connection to move across saidline and toward the frame when the blade encounters a predeterminedresisting force so as to cause said force to pivot the push arm towardthe frame, and means interconnected between said push arm and mold boardfor returning the mold board to a dozing position upon clearing saidresisting force.

2. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at one end thereof pivotally mounting the push arm to saidframe, a mold board having the ground engaging portion thereof mountinga cutting blade, said push arm having a second pivotal connection at theother end thereof pivotally carrying the mold board, operating meanspivotally connected between the main frame and the mold board for movingthe mold board between a dozing and carry position, said push arm secondpivotal connection being located to one side of a line passing throughthe first pivotal connection and said operating means pivotal connectionon the mold board when the mold board is in a dozing position, and meansincluding the operating means permitting the second pivotal connectionto move across said line toward the frame when the blade encounters apredetermined resisting force so that said force pivots the push armabout the first pivotal connection toward the frame and thereby raisesthe mold board to prevent excessive loads from being applied to thefrarne, and spring means connected between said push arm and the moldboard and including said operating means for returning the mold board toa dozing position upon clearing said resisting force.

3. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at one end thereof pivotally mounting the push arm to saidframe, a mold board having the ground-engaging portion thereof mountinga cutting blade, said push arm having a second pivotal connection at theother end thereof pivotally carrying the mold board, operating meanspivotally connected between the main frame and the mold board for movingthe mold board between a dozing and carry position, said push arm secondpivotal connection being located to one side of a line passing throughthe first pivotal connection and said operating means pivotal connectionon the mold board when the mold board is in a dozing position,cooperating stop means formed with said push arm and said mold board forlimiting pivotal movement of the mold board about the second pivotalconnection, and means including the operating means for permitting thesecond pivotal connection to move across said line toward the frame whenthe blade encounters a predetermined resisting force so that said forcepivots the push arm about the first pivotal connection toward the frameand thereby raises the mold board to prevent excessive loads from beingapplied to the frame, and means connected between said push arm and themold board and including said operating means for returning the moldboard to a dozing position upon clearing said resisting force.

4. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at one end thereof pivotally mounting the push arm to saidframe, a mold board having the ground-engaging portion thereof mountinga cutting blade, said push arm having a second pivotal connection at theother end thereof pivotally carrying the mold board, a hydraulicallyoperated jack pivotally connected between the main frame and the moldboard for moving the mold board between a dozing and carry position,said second pivotal connection being located to one side of a linepassing through the first pivotal connection and said jack pivotalconnection on the mold board when the mold board is in a dozingposition, and overload relief means operatively associated with the jackfor permitting the second pivotal connection to move across said lineand toward the frame when the blade encounters a predetermined resistingforce so that said force pivots the push arm about the first pivotalconnection toward the frame and thereby raises the mold board to preventexcessive loads from being applied to the frame, and a spring connectedbetween said push arm and the mold board and coacting with said jack forreturning the mold board to a dozing position upon clearing saidresisting force.

5. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at the one end thereof pivotally mounting the push arm tosaid frame, a mold board having the ground-engaging portion thereofmounting a cutting blade, said push arm having a second pivotalconnection at the other end thereof pivotally carrying the mold board, ahydraulically operated jack pivotally connected between the main frameand the mold board for moving the mold board between a dozing and carryposition, said second pivotal connection being located to one side of aline passing through the first pivotal connection and said jack pivotalconnection on the mold board when the mold board is in a dozingposition, cooperating stop means formed with said push arm and said moldboard for limiting pivotal movement of the mold board about the secondpivotal connection, and overload relief means associated with the jackfor permitting the second pivotal connection to move across said lineand toward the frame when the blade encounters a predetermined resistingforce so that said force pivots the push arm about the first pivotalconnection toward the frame and thereby raises the mold board to preventexcessive loads from being applied to the frame, and a spring connectedbetween said push arm and the mold board and coacting with said jack forreturning the mold board to a dozing position upon clearing saidresisting force.

6. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm having a first pivotalconnection at the one end thereof pivotally mounting the push arm tosaid frame, a dozer blade, said push arm having a second pivotalconnection at the other end thereof pivotally carrying the dozer blade,operating means pivotally connected between the main frame and the moldboard for raising and lowering the push arm, said push arm secondpivotal connection being located to one side of a line passing throughthe push arm first pivotal connection and said operating means pivotalconnection on the dozer blade when the latter is in a dozing position,and means in cluding the operating means permitting the second pivotalconnection to move across said line and toward the frame when the lowerportion of the dozer blade encounters a predetermined resisting force soas to cause said force to pivot the push arm toward the frame, and meansconnected between said push arm and the dozer blade for returning thepush arm to a dozing position upon clearing said resisting force.

7. In combination with a tractor having a main frame, a dozer assemblycomprising push arm means including a push arm pivotally mounted at oneend thereof to the main frame, a dozer blade pivotally supported by theother end of the push arm, operating means pivotally connected betweensaid frame and dozer blade for moving the latter between a carry anddozing position, a latch secured to said dozer blade, a keeper fixed tosaid frame, said latch being located above said keeper when the dozerblade is in the carry position, and means connected between said dozerblade and the push arm to cause said latch to engage said keeper uponfailure of said operating means when the mold board is in a carryposition.

8. In combination with a tractor having a main frame, a

dozer assembly comprising push arm means-including a push arm pivotallymounted at one end thereof to the main frame, a dozer "olade pivotallysupported by the other end of the push arm, a hydraulically operatedjack pivotally connected between said frame and push arm for moving thedozer blade between a carry and dozing position, safety latch meansincorporated with the frame and dozer blade, said latch means comprisinga projection extending from the dozer blade and a keeper formed with themainframe, said projection being located above said keeper when the moldboard is in a carry position, a spring connected between the dozer bladeand push arm to cause said projection to engage the keeper and therebyhold the dozer blade in an elevated position upon failure of said jackwhen the dozer blade is in a carry position.

9. In combination with an overhung tractor having a main frame, a dozerassembly comprising push arm means including a push arm having a firstpivotal connection at one end thereof for pivotally mounting the pusharm to the frame, a mold board having the ground engaging portionrigidly mounting a cutting blade, a second pivotal connection on thepush arm for pivotally supporting the mold board, a hydraulicallyoperated jack pivotally connected between the main frame and the moldboard for moving the latter between a dozing and carry position,cooperating stop means formed with the push arm and mold board forlimiting pivotal movement of the mold board about the second pivotalconnection, a fluid circuit for operating the jack, overload reliefmeans in said circuit for perrnitting the jack to lengthen and shortenwhen the blade encounters a predetermined resisting force so that thepush arm can move about the first pivotal connection towards the frameto raise the mold board, a spring connected between the push arm andmold board for returning the mold hoard toa d zing position when themold board clears the resisting force; a chain mounted between the frameand push arm t6 limit movement of the latter in a direction away fromthe frame, and a latching arrangement for locking said mold board to theframe when the mold board is in a carry position and a failure occurs inthe fluid circuit;

Referenees Cited in the tile of this patent UNITED STATES PATENTS2,117,561 McMaster May 17, 1938 arse 124 Qoa tes July 13, 1939 2,254,151runner Aug; g 1941 2,626,470 Cook et a1. -l Ian, 27, 1953 2,792,650Kenyon May 21, E57 2,804,702 Corser et all. Sept.- 3, 1957 2,910,790Armington a Nov.- 3 195? 3,005,511 Riedy Oct; 24, 1961

1. IN COMBINATION WITH A TRACTOR HAVING A MAIN FRAME, A DOZER ASSEMBLYCOMPRISING PUSH ARM MEANS INCLUDING A PUSH ARM HAVING A FIRST PIVOTALCONNECTION AT ONE END THEREOF PIVOTALLY MOUNTING THE PUSH ARM TO SAIDFRAME, A MOLD BOARD INCLUDING A CUTTING BLADE, SAID PUSH ARM HAVING ASECOND PIVOTAL CONNECTION AT THE OTHER END THEREOF PIVOTALLY CARRYINGTHE MOLD BOARD, OPERATING MEANS PIVOTALLY CONNECTED BETWEEN THE MAINFRAME AND THE MOLD BOARD FOR RAISING AND LOWERING THE MOLD BOARD TO ADOZING POSITION, SAID PUSH ARM SECOND PIVOTAL CONNECTION BEING LOCATEDTO ONE SIDE OF A LINE PASSING THROUGH THE PUSH ARM FIRST PIVOTALCONNECTION AND SAID OPERATING MEANS PIVOTAL CONNECTION ON THE MOLD BOARDWHEN THE LATTER IS IN A DOZING POSITION, MEANS INCLUDING THE OPERATINGMEANS FOR PERMITTING THE SECOND PIVOTAL CONNECTION TO MOVE ACROSS SAIDLINE AND TOWARD THE FRAME WHEN THE BLADE ENCOUNTERS A PREDETERMINEDRESISTING FORCE SO AS TO CAUSE SAID FORCE TO PIVOT THE PUSH ARM TOWARDTHE FRAME, AND MEANS INTERCONNECTED BETWEEN SAID PUSH ARM AND MOLD BOARDFOR RETURNING THE MOLD BOARD TO A DOZING POSITION UPON CLEARING SAIDRESISTING FORCE.